PLEASE HELP I DONT UNDERSTAND?

Okay so I talked to this guy for a few months and things seemed serious although it was long distance. He said he was falling for me but honestly didn't know if he was just filling my head with things. He stopped talking to me for a while out of nowhere TWICE. I started dating this guy that happens to be his best friend but I didn't realize how close they were. He told the friend to go for me and he has changed his opinion immediately upon the friend dating me. We've been together for a good while and still has problems I assume. Can someone explain this?